In this study, the heat utilisation efficiency of all commonly used cookstoves was measured with emphasis placed on natural gas cookstoves. In addition, two improved cookstoves developed by a research institution of Bangladesh (one for biomass and one for natural gas) were studied. The type of cooking vessel (round-bottomed pot and flat-bottomed pan) and the flow rate of gas (power) were the two parameters studied for natural gas cookstoves. The pan was found to give higher efficiencies in all cookstoves. With regard to power it was found that efficiency first increases and then decreases with increasing gas flow rate. An analysis of the design and performance of the existing natural gas cookstoves led to the development of a simple contrivance - a perforated sheet metal shield around the flame and a portion of the cooking vessel. The modified cooking system was found to increase the heat utilisation efficiency. The paper also presents the cost of cooking for different fuel-cookstove combinations.